Currently, in Japan, about 10 million tons of plastics are being discarded annually as industrial waste or general waste, about 55% of which are used effectively. Most of these waste plastics are used as fuels for generating electricity or other heat sources, and not substantially recycled as chemical materials. An unused portion of these waste plastics is disposed of in landfills or subjected to incineration disposal. However, available landfills are becoming tighter year by year and there is a fear of generating dioxins on incineration when resins are mixed such as polyvinyl chloride (PVC) containing a chlorine-based composition.
Under these circumstances, such technology development is ardently desired that waste plastics be subjected to thermal decomposition to obtain a petroleum resource such as fuel oil. More specifically, waste plastics are subjected to thermal decomposition and utilized as a petroleum resource. The thus obtained petroleum resource is used as gasoline, kerosene, light oil or heavy oil. Alternatively, waste plastics are subjected to thermal decomposition to obtain an oil fraction. The oil fraction is further separated into a naphtha fraction which is then used as a raw material for producing chemicals. Various technologies are known by which waste plastics are thermally decomposed to obtain oil fractions as described above.
As technology in which waste plastics having a mixture of resin containing chlorine as a composition, for example, polyvinyl chloride (PVC), are thermally decomposed to obtain an oil fraction, Patent Document 1 has disclosed a method for thermally decomposing waste plastics to petroleum, including a first thermal decomposition step in which high-temperature sands (600° C. to 950° C.) are added to waste plastics and heated to a temperature range from 250° C. to 350° C. to separate chlorine, a second thermal decomposition step in which waste plastics from which the chlorine content is removed are further heated to a higher temperature range (350° C. to 500° C.) with high-temperature sands (600° C. to 950° C.) to effect thermal decomposition, and an combustion step in which gaseous combustible substances formed at the first thermal decomposition step and decomposed residue formed at the second thermal decomposition step is subjected to combustion, wherein at the first thermal decomposition step the waste plastics are brought into contact with fine particles of a neutralizing agent (hydrated lime and the like), a separated chlorine content is coupled to the neutralizing agent, and at least a part of the neutralizing agent coupled to the chlorine content is led to the combustion step together with gaseous combustible substances formed at the first thermal decomposition step. In this conventional technology, FCC waste catalysts are also added to a thermal decomposition area at the second thermal decomposition step at 5 weight % to 35 weight % with respect to waste plastics.    Patent Document 1: Japanese Published Unexamined Patent Application No. 2001-107058